<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<title>B</title>
	</head>

	<body><h1 id="box2"style="display: none;">hahah</h1>
		<div id="box1">
			打开失败，250秒后返回A
		</div>
		<script type="text/javascript">
			var src=document.referrer
			if (src=="") {
				var i=250;
			setInterval(function(){
				document.getElementById("box1").innerHTML="打开失败，"+i+"秒后返回A"
				i--;
			},1000)
			
			}
			
			
			
		</script>
	</body>

</html>